Layers of Earth

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Core

• The core can be divided into two layers (inner core and outer core)
• the inner core is the hottest part of the heat 6200 degrees Celsius
• the outer core and inner core together is responsible for the earth’s magnetism
• the entire core makes up approximately 12% of the total its volume

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Mantle

• The mantle is divided into 2 layers inner/lower mantle and outer/upper mantle
• the inner mantle is solid and upper mantle is semi molten (magma)
• the mantle is about 2900 kilometer stick an makes up nearly eat a percent of the earth’s total volume

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Crust

• The outer most as well as the thinnest layer of the earth (8% of the earth’s total volume)
• it floats upon the softer, denser outer/upper mantle
• there are two types of crusts (oceanic and continental)

The outer mantle and the crust is called the lithosphere. It averages about 100 kilometers in thickness. It is the layer which is the most important to us humans because it affect man’s activities of the formation of landforms.

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Crustal Plates

The Earth’s surface crust is not one massive sheet of rock the earth. The crust is actually broken into many pieces called plates/ crustal plates (oceanic and continental). These crustal plates fit together like a jigsaw puzzle on the earth’s surface. The separation between the plates is called plate boundaries or plate margins.

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Seven Major crustal plates

1. Eurasian plate
2. Indo-Australian plate
3. Nazca plate
4. North America plate
5. South American plate
6. Pacific plate (most active and largest oceanic plate)
7. African plate

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Minor Plates

1. Antarctic plate
2. Cocos plate
3. Caribbean Plate
4. Arabian Plate
5. Iranian plate
6. Philippine plate
7. Scotia plate

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Plate boundaries

There are three types of plate boundaries, that is plates move in three ways in relation to each other because of convection currents in the upper mantle. In some areas of the world, plates move towards each other (convergent/ destructive plate/margin). In other areas plates move away from each other (divergent/ constructive plate margin/ boundary) and finally, some plates slide past each other (transform plate boundary).

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Landforms formed at plate margins

At plate margins/ boundaries convergent, divergent and transform, several features are formed because of the shifting and moving plate tectonics. These features include:

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Earthquakes

These are sudden tremens experienced by plates shifting and moving. Most earthquakes occur at the boundaries where plates meet. Earthquakes experienced at all plate margins/ boundaries.

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Volcanoes

These are sudden tremens experienced by plates shifting and moving. Most earthquakes occur at the boundaries where plates meet. Earthquakes experienced at all plate margins/ boundaries. Volcanoes, a volcano is an opening in the earth’s crust through which lava, volcanic ash and gases escape.

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Divergent plates

Volcanoes can occur at divergent plates, (volcanoes can be formed when plates move apart if this occurs under the sea, is submarine volcano is formed). Magma rises and erupts on the surface forming a volcano/ submarine volcano. If a row of volcanoes are formed along the entire edge of the plate, it is called a volcanic care.

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Convergent plate boundary

When plates converge example boundary of Caribbean and North America, one plate can be pushed beneath another.

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Volcanic Island

These are islands created as submarine volcanoes emerge out of the sea/ ocean water. Volcanic islands can be formed in the following ways:

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Convergent plate boundaries

The eastern Caribbean islands lie on a plate boundary. The North American plate, which is the denser of the 7, sinks beneath the Caribbean plate creating suitable magma conditions to be produced. The magma then rises to the surface of the earth where it may erupt to form a volcano. This process is called subduction, and this is how volcanic islands of the eastern Caribbean were formed

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Divergent plates

Volcanic islands are also formed by volcanic activities on the seabed, often near the boundaries of the divergent tectonic plates. With two plates pull apart, lava erupts to form a submarine volcano. Layers of lava build up until the submarine volcano breaks the seas surface to form an island example Iceland the divergence of North America please on the Eurasian plate.

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Folding & Faulting

A fold is a bend in layers of the earth’s crust. If fault is a crack in the earth’s crust. These are normally found at plate margins and boundaries. A fold is found at convergent boundaries where its layers (crust) experience forces of compression. A fault can be found where the earth’s crust has experienced a crack at convergent, divergent and transform boundaries